This disclosure relates in general to a method and system for monitoring activity, for example monitoring activity proximal to a pipeline, a wellbore or a reservoir associated with hydrocarbon production or transportation and/or carbon dioxide sequestration. More specifically, but not by way of limitation, embodiments of the present invention provide for using an optical fiber as a distributed interferometer that may be used to monitor the activity.
A wide variety of techniques have previously been used to monitor reservoirs, wellbores and/or pipes containing hydrocarbons, such as sub-sea pipelines, transportation pipelines and/or the like. Monitoring of wellbores may often occur during comple3690tion and/or production stages and monitoring may comprise monitoring reservoir conditions, estimating quantities of hydrocarbons (oil and gas), monitoring treatment of the wellbore—which may include monitoring treatment fluids applied to the wellbore, the effects of the treatment fluids and/or the like—monitoring operation of downhole devices in the wellbores, determining conditions in the wellbore, determining condition of the wellbore itself and/or downhole devices, monitoring hydrocarbon production, monitoring completion processes, monitoring stimulation processes, monitoring the formation surrounding the wellbore, monitoring flow of hydrocarbons through a conduit and/or the like.
Reservoir monitoring may involve determining downhole parameters at various locations in a producing wellbore over an extended period of time. To provide for this type of monitoring in a wellbore or the like, wireline tools may be deployed into the wellbore to obtain measurements. Such use of wireline tools is invasive, may affect other operations being performed in the wellbore and/or operations it that might be desirable to perform in the wellbore when the wireline tool is deployed.
In general, wireline monitoring involves transporting the wireline tools to the wellsite, conveying the tools into the wellbores, shutting down the production, making measurements over extended periods of time and processing the resultant data. Use of wireline tools may be expensive, cause production delay and because the wireline tools may, in certain circumstances, have to be removed from the wellbore for other wellbore procedures to occur, may not provide for detecting/analyzing continuous data from the wellbore. Similarly, with conduits containing hydrocarbons, periodic testing along/through the conduit as to the condition of the conduit, analysis of any material in and/or flowing in the conduit and/or analysis of the hydrocarbons in the conduit may also be invasive, expensive, cause production/transportation delay, only provide for sporadic monitoring, only provide for disjointed monitoring of specific locations along the conduit and/or the like.
With regard to the production stages of a well, a wide range of intervention production logging tools exist which may be lowered into a well and measure flow conditions at a known location. These tools may be moved through the well to provide multi-point measurements. These tools are not ideally suited to monitoring simultaneous events at multiple locations or for long period deployments. In addition, it may be difficult to log below wellbore architecture like valves, packers or pumps. Also the very fact of installing such a tool may change conditions such that the measured results are not representative of those when the tool is not present.
With regard to the wellbore, monitoring of sand in the wellbore may be of high important for certain types of wellbores, since the production of sand in the wellbore may have detrimental effects on production of hydrocarbons from the wellbore. Sand may be considered to be any type of particulate matter in the wellbore. Sand may cause such detrimental effects as clogging well lines, adversely affecting pump operation, causing corrosion and/or erosion to pipes and associated equipment and/or the like. As such, sand monitoring along the wellbore may be necessary so that steps may be taken to counter its possible adverse effects.
Additionally, with regard to wellbore processes, gravel packing may be a process that it is desirable to monitor and to manage. The gravel packing process involves pumping a gravel slurry along a length of the wellbore and then allowing the gravel to drop-out filling the wellbore around a sand screen disposed in the wellbore. Typically, the lower section of the wellbore may be filled from heel to toe (often referred to as the Alpha wave) then the upper section from toe to heel (often referred to as the Beta wave).
A full understanding of how and where gravel deposition is occurring in real-time may provide the knowledge required to optimize the gravel placement process. Downhole monitoring of the treatment may show when gravel deposition along the screen is not progressing as desired, with either areas of low gravel concentration (possibly leading to voids) or very high concentrations (possibly leading to premature bridging). When problems with the pack deposition are identified, treatment pumping parameters may be altered to help rectify the situation. Pump rate, fluid viscosity or gravel concentration may all be managed if real-time monitoring is occurring to improve the gravel deposition. Downhole hardware may also be customized to allow for altered flow paths based on information about the gravel bed development.
In addition to monitoring many other processes and procedures in a wellbore, such as gas lift monitoring, flow obstacles, device operation, stimulation processes etc., it may also be desirable to monitor transportation of hydrocarbons through pipelines for flow assurance purposes and/or the like. Further, with increased attention to and development of carbon dioxide sequestration in subsurface locations, a permanent or semi-permanent type sensor for monitoring the transportation and subsurface sequestration of carbon dioxide is also desirable.